The present invention relates generally to apparatus and methods for shrink treating a traveling textile fabric web and, more particularly, to such an apparatus and method adapted for treating both woven and knitted fabrics.
In the finishing of textile fabrics, particularly fabrics which are susceptible to shrinkage when laundered, it is known to subject such fabrics to a shrinkage treatment to improve the dimensional stability of the fabric. In conventional equipment for this purpose, the fabric web to be treated is initially passed through an intake mechanism wherein traction and guide rolls elevate the fabric web and then direct it downwardly through a device for spreading the fabric into flat open width form followed by a spray or similar device for wetting the fabric to a predetermined degree. The flat wetted fabric is then fed into a compressive shrinkage unit wherein the fabric is compressed between a rotating drum and a traveling elastic belt trained in peripheral compressive contact with the drum for mechanically shrinking the fabric. The fabric is passed over another stationary fabric spreading device after leaving the shrinking unit and is then delivered to a calendering mechanism wherein the fabric is dried in flattened sheet form between a large diameter heated calender drum and a traveling endless belt of felt material trained in peripheral contact with the calender drum about a substantial extent of its circumference. Following the calendering mechanism, the fabric is guided over several guide rollers to a cuttling device for pleated folding of the fabric or to a winder for winding the fabric about a storage tube.
The shrink treatment apparatus and process described above produces good results when utilized for most woven fabrics but, for a number of reasons, is generally unsuitable for shrinkage treatment of knitted fabrics. First of all, knitted textile fabrics typically have a greater capability for moisture retention than woven fabrics and, accordingly, in shrink treating knitted fabrics, a markedly lesser degree of fabric wetting is necessary. For example, woven fabrics generally are wetted for shrink treatment to approximately a 10% moisture content by weight of the fabric, whereas knitted fabric should not be wetted to greater than a 5% moisture content by fabric weight for proper shrink treating results. As a result, the spray wetting of fabrics in conventional shrink treating apparatus as described above is unsuitable for processing knitted fabric.
Further, the downward travel of the elevated fabric through the fabric spreading device in conventional shrink treating equipment, while important and necessary for opening woven fabric to a flat full-width sheet form, causes knitted fabric to contract widthwise into drape-like folds. Therefore, knitted fabric cannot be effectively smoothed and held in flat open-width form by the intake mechanism of conventional shrinkage equipment, as is necessary for effective shrink treatment.
A further difficulty in shrink treating knitted fabric utilizing conventional shrinkage equipment of the above-described type is that, even if knitted fabric is wetted only to the reduced moisture content within the acceptable range, the fabric still should be dried considerably less by the calendering mechanism following shrinking than when processing woven fabric. In this regard, it is desirable that knitted fabrics should not be fully dried within the shrinking system but instead should be allowed to dry gradually to achieve good shrinking results. Thus, in contrast to the processing of woven fabrics, knitted fabrics should not be overdried but rather should retain some percentage of moisture when delivered from the shrinking mechanism. Accordingly, in using conventional equipment for shrink processing of knitted fabric, the calendering mechanism must be operated to produce a significantly reduced amount of drying energy in comparison with the processing of woven fabrics in order to reduce the extent of the drying of knitted fabrics.
As mentioned above, in conventional shrink treating equipment, the fabric is guided over a series of guide rollers to travel from the calendering mechanism to a cuttler or a winder. Typically, the guide rollers are positioned above the calendering mechanism so that the fabric follows an upward path from the calendering drum. However, knitted fabrics tend to undergo a degree of stretching when transported along an upward path following shrinking, negating a considerable amount of the fabric shrinkage achieved.
Thus, since conventional shrinking equipment designed for woven fabric is generally unsuitable for shrink treatment of knitted fabrics, specialized shrinking equipment has been developed especially for the shrink processing of knitted fabric, but as will be understood considerably greater expense is incurred in acquiring, operating and maintaining separate shrinking systems for woven and knitted fabrics. To avoid the additional expenses involved, it is possible to make structural alterations in conventional shrinkage treating equipment designed for woven fabrics in order to convert the equipment for use with knitted fabrics. However, such modifications are economically justifiable only if the equipment is to be operated as altered for a relatively long period of time, e.g., one month or more. Numerous textile factories, such as finishing jobbers, must instead shrink treat woven and knitted fabrics in frequent alternation and accordingly, such factories are forced therefore to acquire separate shrinking equipment for woven and knitted fabrics.